One of the most pressing challenges in the design of an accumulator is the fabrication of a light weight and compact device that may be used in various industries. Hydraulic accumulators are energy storage devices commonly used to provide supplementary fluid power and absorb shock. One particularly interesting recent application of these devices is regenerative braking. Although a theoretically appealing concept, hydraulic regenerative braking is difficult to implement due to some major inherent limitations and non-ideal properties of conventional accumulators.
Currently available accumulators include gas bladder accumulators and piston accumulators with a gas pre-charge, each of which use gas for energy storage and, therefore, have greater gravimetric energy density than their spring piston counterparts. However, such accumulators present problems to be solved. In these accumulators, a gas, separated by a bladder or a piston, occupies a certain volume of a container which is otherwise filled with a fluid, typically hydraulic fluid. As fluid is forced into this container, the gas inside the separated volume is compressed and energy is stored in this compressed gas. Such accumulators are subject to two serious drawbacks: 1) inefficiency due to heat losses, and 2) gas diffusion through the bladder into the hydraulic fluid. The drawback of inefficiency via heat loss is perhaps addressable through an isothermalizer foam inserted inside the gas bladder, but the gas diffusion issues gives rise to high maintenance costs associated with “bleeding” the gas out of the fluid often.
What is needed is an accumulator that very efficiently stores energy within a very limited space. While doing so, such an accumulator must be light weight. Conventional accumulators fail to fully address these problems and fail to provide the needed features.